1. Field of the Invention
This invention relates generally to injection molding and, more particularly, to a valve gated hot runner injection molding apparatus for tight pitch, single- or multi-material applications.
2. Background of the Invention
A valve gated injection molding apparatus is well known, as shown and described in U.S. Pat. No. 4,380,426 incorporated herein in its entirety by reference thereto. Usually a valve pin has a cylindrical or tapered front end and reciprocates between a retracted open position and a forward closed position in which the front end is seated in a gate. In some applications, the valve pin functions in the reverse direction and closes in the retracted position.
A valve gated injection molding apparatus for coinjecting and/or sequentially injecting two different materials through a single gate with multiple valve pins into a mold cavity is also well known, as shown and described in U.S. Pat. No. 5,238,378 incorporated herein in its entirety by reference thereto. For a greater level of control over the gating process, each individual valve pin may be independently controlled by separate actuation units.
Also well-known in the art is a multi-cavity valve gated injection molding apparatus having a plurality of nozzles, wherein each nozzle body is provided with a plurality of equally spaced valve pin bores with a corresponding plurality of valve pins. Such an apparatus in shown and described in U.S. Pat. No. 6,162,044 incorporated herein in its entirety by reference thereto. Each nozzle of the apparatus includes multiple valve pins, but all of the valve pins are controlled by a single actuation unit.